In batteries with electrodes of this type, a problem arises when conducting the current from the supporting structure to a battery terminal. A current tab or current lead out plate conducts current from the structure to the terminal. Conventional structural bodies are made from sintered metal powder and contain a metal carrier, which projects from the sintered structure at one edge. Perforated plates, expanded metal or metal networks are used as carriers. The current lead out tab can be attached to that portion of the carrier which projects from the sintered structure. Electric spot welding or roll welding are methods of attachment.
Metallized bodies of a fibrous nature are particularly suitable as electrode structures due to their high porosity. An electrode structure made from a metallized felt is illustrative because it exhibits a porosity of approximately 85%.
The body forming the electrode structure is produced by electrodepositing a sufficiently thick metal coating, for example of Ni or Cu, onto an electrically conductive textile body. The conductive textile body can be a carbon fiber felt, a material woven from carbon fibers or a textile such as felt, a woven material or a fibrous web. This textile is metallized using conventional PVD or CVD vapor deposition techniques or by using a conventional chemical process not involving electric current. See German Pat. Nos. 2,251,160 and 2,418,742, which are hereby incorporated by reference.
The structural bodies, produced in this way, require no metal carrier, such as expanded metal or perforated plate carrier. These structural bodies exhibit good intrinsic stability and good current carrying capacity. Due to the high porosity of the metal fiber structures, attachment of the current tab directly to the supporting structure by spot welding, seam welding by rollers, or by riveting is difficult because the structural body is substantially compressed where the support and tab are joined during the welding or riveting operation. Also, there is the danger of fiber breakage near the connection so that both the mechanical integrity of the connection and its current transfer capabilities are degraded.
The present invention seeks to overcome the disadvantages of the prior art. Thus, the object of this invention is to provide a process which enables current tabs to be securely connected to a highly porous structural body, while simultaneously ensuring that these connections retain their mechanical integrity and current capability by having low electrical transition resistance.
These and other objects, features and advantages of the present invention will become more apparent from the following description when taken in connection with the accompanying examples which show for purposes of illustration only an embodiment in accordance with the present invention.